The present disclosure relates asset management systems and methods that formulate schedules for inspection, maintenance, repair, replacement, and remedial activities while optimizing total costs. The optimization may occur in a manner that accounts for risk-weighted costs, multiple degradation modes, inspection failures, schedule constraints, and return on investment (ROI) requirements.
The term “plant” as used herein means the equipment (including machinery, tools, instruments, fixtures, and the buildings containing them) necessary for an industrial or manufacturing operation. Petroleum refineries, plastics companies, chemical manufacturers, and water processors are examples of industrial operations that employ a plant to produce their products. FIG. 1 shows an illustrative plant and it is described here to provide some context for understanding the novel systems and methods of the present disclosure. It is important to note that the disclosed systems and methods have wide applicability and are in no way limited by the following description of an illustrative plant.
FIG. 1 is taken from issued U.S. Pat. No. 6,350,354 (Neuman et al.), and full details of its operation can be found there. It is briefly described here to illustrate the complexity of even a relatively simple industrial plant and to demonstrate some of the challenges faced by a plant manager trying to operate the plant in an economical fashion.
FIG. 1 is a schematic representation of a modular solvent extraction plant. Piping 10 transports a raffinate fluid onto a leach area 12, where it extracts metal from the ore found there. Line 14 and pump 16 transfer the pregnant leach solution to a plug flow contactor 18, where it mixes with organic solution from line 22. (A pump 20 in line 22 draws the organic solution from later process stages and make-up fluid from line 39.) Contactor 18 forms a mixed emulsion of the two fluids, which exits through piping 24 to reactor 26. After a dwell time in the reactor, the mixed emulsion travels through piping 27 to a separator 28. Separator 28 separates the extraction emulsion into a raffinate and a loaded organic solution. Piping 30 transports the raffinate to raffinate coalescer 32, which removes organic entrainment and expels it via line 34. The raffinate fluid is returned to the leach area 12 via piping 10, along with aqueous “make-up” solution from piping 31.
The loaded organic solution from separator 28 flows through piping 36 to contactor 100. Piping 107 feeds the mixture leaving contactor 100 into scrub station separator 108. Scrub station separator 108 separates the aqueous solution and the loaded organic solution. Optionally, a coalescer unit may be attached to scrub station separator 108 so as to further remove any aqueous entrainment from the organic solution. Piping 110 transports aqueous solution from scrub station separator 108. Piping 110 is connected to piping 102, allowing a pump 104 to recycle aqueous through the contactor 100. Bleed stream 114 allows aqueous solution in piping 100 to exit the system. Line 106 (coupled to input piping 31) transports make-up aqueous solution to line 102.
A pump 42 conveys loaded organic solution from scrub station separator 108 via piping 112 to plug flow contactor 44 for stripping. A separate pump 47 provides an electrolyte solution to contactor 44 via piping 46. Contactor 44 mixes the loaded organic solution and the electrolyte solution to form a second mixed emulsion. Line 48 transports this mixed emulsion from contactor 44 to second reactor 50, which allows for most of the dwell time of the emulsion. Line 51 transports the mixed emulsion from reactor 50 to second separator 52. Separator 52 separates the mixed emulsion into a barren organic solution and a metal electrolyte solution. Pump 20 pumps the barren organic solution, which is in line 22, from separator 52 to contactor 18 for recycle. Piping 54 transports the metal electrolyte solution from separator 52 to electrolyte coalescer 56. Piping 58 transports recovered organic entrainment from electrolyte coalescer 56. Piping 59 transports the metal electrolyte solution from coalescer 56 to an electrowinning tankhouse 60 via the tankhouse piping circuit. Metal cathodes are obtained from electrowinning tankhouse 60 and are represented as exiting tankhouse 60 by line 64. Piping 46 transports electrolyte solution from electrowinning tankhouse 60 to contactor 44 via pump 47 for recycle. Line 62 feeds an electrolyte make-up solution into electrowinning tankhouse 60. Supporting components, such as holding tanks required for surge capacity and mixers for treating the process streams with additives are also needed, but are not shown here.
The various fluids employed in this process can be expensive and/or harmful to the environment or workers who are inadvertently exposed to them, and thus the plant manager is motivated to avoid leaks. Moreover, the plant manager is motivated to maximize the return on investment, which generally requires minimizing downtime and avoiding process inefficiencies in the process. Thus, to the extent that it is economically feasible, the plant manager will perform inspections to monitor corrosion, thinning, cracking, creep, mechanical failure, internal component degradation, and fouling, and will take corrective action. However, when managing hundreds or thousands of components having varying levels of criticality and varying rates of degradation, while relying on inspection methods with varying degrees of success at detecting different degradation modes, plant managers routinely rely on the most conservative approach to inspection and maintenance that their budgets will allow. This approach hurts the profit margin and, if the budget is too tight, unnecessarily increases the risk of catastrophic failure and the corresponding costs associated therewith. Moreover, this approach fails to quantify the benefit of equipment improvements or modifications versus continual inspection and repair efforts.
U.S. Pat. No. 4,998,208, entitled “Piping Corrosion Monitoring System Calculating Risk-Level Safety Factor Producing an Inspection Schedule” by R. P. Buhrow et al., discloses a computerized system for calculating subsequent inspection dates for piping circuits based ultimately on previous inspection measurements, subjective evaluations of risk, and suggested safety factors. The Buhrow patent is representative of the existing management proposals of which the applicants are aware. Existing asset management techniques rely heavily on heuristic approaches and uniformly fail to determine an optimum, quantitative balance between economic costs and benefits (such as risk amelioration) when formulating an asset management plan.